Total blood volume is about 4.5 to 5 liters in adult human being

i.The defibrinated plasma is called serum, which lacks coagulation factors including prothrombin and fibrinogen. ii.Total protein content of normal plasma is 6 to 8 g/100 ml. iii.The plasma proteins consist of albumin (3.5 to 5 g/dl), globulins (2.5-3.5 g/dl) and fibrinogen (200-400 mg/dl). The albumin: globulin ratio is usually between 1.2:1 to 1.5:1. iv.Almost all plasma proteins, except immunoglobulins are synthesized in liver.

ELECTROPHORESIS

The term electrophoresis refers to the movement of charged particles through an electrolyte when subjected to an electric field.

Serum electrophoretic patterns

1.Chronic infections: The gamma globulins are increased, but the increase is smooth and widebased. 2.Multiple myeloma: In para-proteinemias, a sharp spike is noted and is termed as M-band. This is due to monoclonal origin of immunoglobulins in multiple myeloma 3.Nephrotic syndrome: All proteins except very big molecules are lost through urine, and so alpha-2 fraction (containing macroglobulin) will be very prominent.

ALBUMIN The name is derived from the white precipitate formed when egg is boiled

Functions of Albumin

1. Colloid Osmotic Pressure of Plasma

Proteins cannot easily escape out of blood vessels, and therefore, proteins exert the effective osmotic pressure'. It is about 25 mm Hg The maintenance of blood volume is dependent on this effective osmotic pressure.

Transport Function Albumin is the carrier of various hydrophobic substances in the blood.

i Bilirubin and nonesterified fatty acids are specifically transported by albumin. ii. Drugs (sulpha, aspirin, salicylates, dicoumarol, phenytoin). iii. Hormones: Steroid hormones, thyroxine. iv. Metals: Calcium, copper and heavy metals are nonspecifically carried by albumin.

NutritionalFunction All tissue cells can take up albumin by

pinocytosis. It is then broken down to amino acid level. Albumin may be considered as the

transport form of essential amino acids from liver to other tissues.

Blood Brain Barrier Albumin-fatty acid complex cannot cross blood brain barrier and hence fatty acids cannot be taken up by brain. The bilirubin from albumin may be competitively replaced by aspirin and such other drugs. In newborns, bilirubin is already high. There is a probability that free bilirubin is deposited in brain leading to kernicterus and mental retardation.

Edema Hypoalbuminemia will result in tissue edema

i. Manutrition, where albumin synthesis is depressed (generalised edema) ii. Nephrotic syndrome, where albumin is lost through urine (facial edema). Presence of albumin in urine is called albuminuria. Large quantities (many grams per day) of albumin is lost in urine in nephrotic syndrome. Small quantities are lost in urine in acute nephritis, and other inflammatory conditions of urinary tract. Detection of albumin in urine is done by heat and acetic acid test.

iii. Cirrhosis of liver (mainly ascites). Albumin synthesis is decreased. iv. Chronic congestive cardiac failure: Venous congestion will cause increased hydrostatic pressure and decreased return of water into capillaries and so pitting edema of feet may result.

Albumin-Globulin Ratio In hypoalbuminemia, there will be increase in globulins which are synthesised by the reticuloendothelial system. Albumin-globulin ratio (A/G ratio) is thus altered or even reversed. This again leads to edema.

TRANSPORT PROTEINS Blood is a watery medium; so lipids and lipid soluble substances will not easily mix in the blood. Hence, such molecules are carried by specific carrier proteins Albumin Pre-albumin or Transthyretin Thyroxine binding globulin (TBG) Retinol binding protein (RBP) Transcortin or cortisol binding globulin

(CBG) Transferrin

ACUTE PHASE PROTEINS The level of certain proteins in blood may increase 50 to 1000 folds in various inflammatory and neoplastic conditions. Such proteins are acute phase proteins. Important acute phase proteins are described

C-Reactive Protein (CRP) Ceruloplasmin Wilson's Disease

STRUCTURE OF IMMUNOGLOBULINS

Immunoglobulin is abbreviated as Ig. The terms gamma globulin and immunoglobulin are not synonymous. Gamma globulin is the term describing its mobility in electrical field. Most of the immunoglobulin's have the gamma mobility; but some may move along with beta or even with alpha globulins. Immunoglobulin is a functional term, while gamma globulin is a physical term. In 1962, Rodney Porter and Gerald Edelman independently proposed the structure for immunoglobulin molecule, for which both of them were awarded Nobel prize in 1972.

Heavy and Light Chains The structure of IgG molecule. It is made up of 2 heavy (H) chains and 2 light (L) chains, combined through disulfide bridges. In the case of IgG, H chains are composed of 440 amino adds and L chains made up of 214 amino acids. Depending on the heavy chain make up, the

immunoglobulin's are differentiated into 5 major

1. Immunoglobulin G (lgG) is made up of heavy chain γ (gamma) 2. IgM has µ (mu) heavy chain 3. IgA has α (alpha) heavy chain 4. IgD contains (delta) 5. IgE heavy chain is called ε (epsilon).

The light chains are either Κ (kappa) or λ (lambda) in all the classes. For

example, IgG may consist of either γ2 κ2 γ2 λ2

Variable and Constant Regions Both the heavy and light chains contain relatively variable (V) and constant (C) regions with regard to their amino acid composition. VL and CL are the general terms for these regions on the light chain; while VH and CH specify variable and constant regions on the heavy chain

At the amino terminal end, about 100 amino acids in light chains and in heavy chains constitute the variable region. Here the amino acid sequence can vary in Hand L chains, so that the body could synthesise enormous varieties of different proteins.

Different Classes of Immunoglobulins 1. Immunoglobulin G (lgG) a. IgG contains two heavy chains and two light chains; heavy chains being of gamma. Due to its sedimentation coefficient, it is sometimes referred to as 78 Ig. b. It is the antibody seen in secondary immune response. c. It can pass from vascular compartment to interstitial space. It can cross placental barrier, and protects the new born child from infections.

2. Immunoglobulin M (lgM) IgM are macroglobulins or 19S immunoglobulins. Five subunits, each having 4 peptide chains (total 10 heavy chains and 10 light chains) are joined together by a J-chain polypeptide It can combine with 5 antigens simultaneously, and so IgM is very effective for agglutinating bacteria. Being a large molecule, it cannot come out of vascular space. IgM are the predominant class of antibodies in primary response.

3. Immunoglobulin A (lgA) a.IgA usually are dimers (total 4 heavy chains and 4 light chains). The J chain connects the dimers. b.They are the secretory antibodies seen in seromucous secretions of gastrointestinal tract, nasopharyngeal tract, urogenital tract, tears, saliva, sweat, etc. The dimers are stabilised against proteolytic enzymes by the secretory piece.

4. Immunoglobulin E (lgE) They mediate allergy, hypersensitivity and anaphylaxis. They have the property to fix on mast cells and basophils. When certain antigens such as penicillin are injected a few times, IgE class antibodies are produced which anchor on mast cells. When the same antigen is injected next time, the antigen fixes on cell surface antibodies, causing mast cell degranulation, and release of histamine and slow reacting substance.

PARAPROTEINEMIAS 1. Multiple Myeloma (Plasmacytoma) i. When Ig-secreting cells are transformed into malignant cells, one clone alone is enormously proliferated. Thus, Ig molecules of the very same type are produced in large quantities. ii. This is seen in electrophoresis as the myeloma band or monoclonal band or M band with a sharp narrow spike (Fig. 13.1). iii. Multiple myeloma is characterized by paraproteinemia, anemia, lytic bone lesions and proteinuria. iv. Bone marrow examination reveals large number of malignant plasma cells. Bone pain and tenderness are the common presenting complaints. Spontaneous pathological fracture of weight bearing bones, rib and vertebrae may occur.

2. Bence Jones Proteinuria Henry Bence Jones described it in 1848. i. This disorder is seen in 20% of patients with multiple myeloma. ii. Monoclonal light chains are excreted in urine. iii. The Bence Jones proteins have the special property of precipitation when heated between 45°C and 60°C; but redissolving at higher than 80°C and lower than 45°C.

3. Hypergammaglobulinemia This disorder can occur in: i. Chronic infections, where antibody production is high. Examples are leprosy, tuberculosis, malaria and subacute bacterial endocarditis

ii. Aberrant immune reactions such as rheumatoid arthritis, collagen disorders, glomerulonephritis, and such autoimmu ne disorders where cryoglobulins may also be present. iii. Paraproteinemias such as in multiple myeloma

Ceruloplasmin contains copper; it is decreased in Wilson's hepato lenticular degeneration. Blood fibrinogen level is 200-400 mg/dl. Hemophilia is due the deficiency of anti-hemophilic globulin (AHG) or factor VIII. Immunoglobulins are classified into 5 classes; IgG, M, A, 0 and E. IgM is seen in primary antibody response. IgA is secretory antibodies. IgE is associated with allergy and anaphylaxis.